Which statement about heavy timber construction is true?

• A. It requires encasement to achieve fire resistance
• B. It has no fire resistance
• C. It has high fire resistance due to mass
• D. It is prohibited in modern codes

Answer: (C)

Heavy timber construction relies on the inherent fire resistance of large wooden members. When exposed to fire, the outer layer of wood chars and acts as an insulating shield, while the massive interior takes longer to heat up. This slow heat transfer means the structural core maintains strength longer, giving heavy timber its high fire resistance. Because of this mass and charring behavior, it can meet fire‑resistance requirements without encasement in many designs, though specific ratings depend on size and code requirements. The idea that it has no fire resistance or that it’s prohibited in modern codes isn’t accurate, and the main truth is that its substantial mass provides substantial, intrinsic fire resistance.